I just bought a 1991 535i. Its a beautiful car. Has suspension upgrades and is chipped. Its a 5 speed and drives like a brand new car. I know it has had a valve adjustment and many other small things. How often do the valves need adjusting? Anyone know the stock horse power/tourqe and 0-60/1/4 mile times? I have had porsches in the past so im used to maintence. Thanks